Fluid cooled apparatus with natural and forced cooling



June 4, 1957 w. c. sEALEY FLUID COOLED APPARATUS WITH NATURAL AND FORCEDCOOLING Filed Jan. 7. 1953 2 Sheets-Sheet 1 web. M mm June 4, 1957 w. c.sEALl-:Y

2,794,625 FLUID COOLED APPARATUS WITH NATURAL AND FORCED COOLING lFiled-Jan. '7. 195s 2 Sheets-Sheet 2 United States Patent O FLUID COOLEDAPPARAT US WITH NA AND FGRCED COOLING William C. Sealey, Wauwatosa,Wis., assignor to Allis- Chalmers Manufacturing Company, Milwaukee,`Wis.

Application January 7, 1953, Serial No. 329,977

13 Claims. (Cl. 257-491) This invention relates generally to apparatusprovided with fluid by which heat is dissipated and particularly toelectrical apparatus, such las transformers, that are embodied incasings having heat dissipators and provided with cooling fluid, such asinsulating oil, which is circulated under certain conditions by naturalconvection and under other conditions by a pump for increasing the rateof ow of the fluid through the heat dissipators.

Various heat exchange means or systems have been provided for coolingelectrical apparatus, such as transformers. ln those systems heat of thetransformer is transferred from the coils and core thereof to the oil orother cooling fluid by conduction, thereby causing that uid to flow byconvection to eventually transfer the heat by conduction to the materialof the casing and radiators attached thereto, from which the heat istransferred by radiation and conduction to the cooling air surroundingthe casing and radiators. ln such apparatus, where the transformer heatsthe cooling uid to cause it to ow by convection in a natural circulatorypath upwardly through the transformer disposed in the casing anddownwardly through the radiator external of the casing, the system willbe generally referred to hereinafter as a self-cooled system yhaving aself-cooled rating. And where a uid pump is provided to increase therate of circulation of fluid, the system will be referred to as forcedfluid, having a forced huid cooled rating.

While it has been suggested that encased transformers may have boththese systems adapted thereto, such transformers have had to be providedwith separate Vheat dissipators for the two systems involvingconsiderable expense, or the flow of fluid by natural convection in theself-cooled system has been considerably restricted because of passingthrough the pump of the other system, or a bypass and valves orexcessively large passages in the pump have had to be provided so as notto impede the natural convection system. lt has also been suggested thatthe pump and parts of its system may be embodied in the transformercasing, but that results in 'an increase of the size of the casing andcomplicates the design of the transformer because of the addedinsulation problems. And naturally, it is impractical to changetransformers embodying only a self-cooled system to `add an internallyarranged pump of a forced flow system.

ln accordance with the teachings of this invention those two systems maybe combined in an improved way eliminating the necessity for separateheat exchangers in the forced fluid ow system and eliminating thenecessity of an internal pump. The above mentioned disadvantages areavoided by constructing and larranging the apparatus, its casing andcooling systems in accordance with this invention in such manner as toprovide a uid pump preferably disposed externally of the casing andarranging that pump and its intake and discharge with respect to theradiators so that the natural convection ilow of the fluid in theself-cooled system does not pass through the pump but still utilizes thesame radiators as the forced fluid flow system Without providing 'a-specially arranged valve or a bypass of the pump. Further, inaccordance with the teaching of this invention apparatus now providedwith conventional radiators of only a self-cooled system may relativelyeasily and with minimum expense be provided with `an efficient forcedhuid system without additional radiators, valves or bypasses and withoutlessening the effectiveness of the self-cooled system.

It is therefore an object of this invention to provide an improvedcooling system for apparatus subject to changes in temperature designedto have both the so-called forced uid `cooled rating 'and self-cooledrating.

Another object of this invention is to simplify the structure andconstruction of cooling system apparatus of transformers, or the like,designed to have self-cooled rating and forced fluid cooled rating.

Still another object of this invention is to provide for transformers orthe like encased apparatus, selfcooled rating Iand forced uid cooledrating by such means for circulating the fluid in the forced uid systemthat does not interfere with the self-cooled rating and thereby does notlessen the effectiveness of the self-cooled system and in which theself-cooled system of the encased electrical apparatus is as e'icientand inexpensive as a similar selfcooled system designed for a similarelectrical apparatus not provided with a forced uid system.

And another object of this invention is to provide an inexpensive forceduid apparatus to be easily and inexpensively added to self-cooledtransformers.

Objects and advantages other than those above set forth will be apparentfrom the following description when read in connection with theaccompanying drawings, in which:

Fig. l is a diagrammatic view in elevation of an encased core typetransformer made in accordance with the teaching of this invention. Thetransformer casing and part of one Winding of the transformer are shownin section;

Fig. 2 is an elevation view of a shell type transformer disposed in aliquid filled cas-ing and embodying a modication of the cooling systemarranged in accordance with the teaching of this invention. Thetransformer and casing are diagrammatically illustrated and shown insection;

Fig. 3 is a diagrammatic illustration in elevation of anothermodification of a cooling system 'arranged in accordance with thisinvention, adapted to an encased transformer of the shell type which isshown in section;

Fig. 4 is a diagrammatic illustration in elevation of still anothermodification of Ia cooling system arranged in accordance with thisinvention, also adapted to an encased transformer of the shell typewhich is shown in section;

Fig. 5 -is lanother diagrammatic illustration in elevation of an encasedtransformer of the shell type which is shown in section with va coolingsystem adapted thereto in accordance with the teaching of thisinvention. While this cooling system is similar to that shown -in Fig. lthe bafe arrangement in the casing is modified to provide better coolingof the shell type transformer disposed as shown in this gure;

Fig. 6 is a diagrammatic illustration in elevation of a modied showingof an encased transformer of the shell type shown in section, with theheat dissipating radiating surfaces comprising the external walls of thecasing; and

Fig. 7 is a cross sectional view taken along the line VIl-Vll of Fig. 1.

An electrical apparatus is disposed in a casing provided with heatdissipating means through which the cooling iluid is directed. Suitabledissipating means may be associated with the casing to be substantiallya part thereof with adequate bafing to effect lluid paths passing alonga wall surface which radiates heat to the surrounding air. Theseauxiliary paths may be made in any suitable manner as by baling meanswithin the casing but preferably are illustrated as radiators the endsof which ar@ attached to the main portion of the casing at differentlevels; whether these auxiliary paths be along an external wall surface,or through a radiator they may be said to be auxiliary portions of thecasing. In Fig. l, a core type transformer 11 is disposed in a casing12, with suitable heat dissipating radiators 13 and 14 disposed onopposite ends of the casing, being connected in iluid exchange relationwith the casing by upper iluid conduits 21 and 22, respectively, and bylower iluid conduits 23 and 24, respectively. A cooling and insulatingiluid 16 illls the casing. f the iluid is a liquid such as oil, .itslevel is above the top of the upper iluid conduits, but a cooling andinsulating gas would-lill the entire casing. Additional radiators may bedisposed along the sides of the casing, having conduit connections tothe casing at 19 and 20. Y e

As illustrated in Figs. l and 7, windings of the transforzner compriseaxially spaced superposed disk coils 27, which are separated by radiallyextending arcuately spaced disk spacers 26. Adjacent spacers 26 combinewith the disk coils 27 to form horizontally disposed ducts 35 betweenthe disk coils 27 and disk spacers 26. In the bore formed by thesuperposed disk coils 27 are concentric cylindrical barriers 29 and 29which are separated to form vertically disposed ducts 28 and 28. Thespacing of these cylindrical barriers may be maintained by verticalspacing rods 30 between the barriers 29 and 29 and additional verticalspacing rods 30 between outer barrier 29' and the superposed disk coils27. Inner vertical duct 28 is formed between barriers 29 and 29 andouter vertical duct 2S is formed between disk coils 27 and the outerbarrier 29. In abutment with the top disk spacers 26 and the top of thecylindrical barriers 29 and 29 are radially extending arcuately spacedend spacers 25. Adjacent end spacers 25 combine with the top disk coil27 to form horizontally disposed inlet ducts 15. These inlet ducts 15form passages for the flow of cooling iluid from the natural passagewaysin the casing 12 to the vertical ducts 28 and 28. In similar mannerradially extending arcuately spaced end spacers 25 are positioned inabutment with the bottom disk coil 27 and bottom of the cylindricalbarriers 29 and 29 to form horizontally disposed outlet ducts 15.

A part of the iluid entering inlet ducts 15 ilows into and downwardlythrough the outer vertical duct 28. The remainder of the iluid ilowingthrough inlet ducts 15 ilows into and downwardly through the innervertical duct 28 and emerges from the outlet ducts'15.

Fluid also enters the horizontal ducts 35 in the upper half of thewinding and ilows into the outer vertical duct 28. Part of the fluid inthe outer vertical duct 28 will emerge from the horizontal ducts 35 inthe lower half of the winding. The remainder of the iluid in the outerduct will emerge from the outlet ducts 15'.

Batlle means is provided in the casing to aid in directing the ilow offluid to the ducts in the windings. In this instance, a horizontallydisposed baille 31 extends from the approximate outer peripheral surfaceof the winding 17 to the adjacent sides of the casingY intermediate theupper and lower iluid conduits 21 and 23, providing a relatively smallpassageway 33 between the baille and outer surface of the winding. Asimilar horizontally disposed baille 32, which may be integral with`baffle 31, is similarly arranged with respect to winding 18 and thesides of the casing adjacent thereto, extending from the approximateouter peripheral surface of the winding to the adjacent sides of thecasing intermediate vthe-upper and lower iluid conduits 22 and 24.

ln Fig. l suitable means is provided for circulating the cooling iluidunder suilicient head to move that iluid at a considerably increasedrate through the radiators 13 and 14 when it is necessary to dissipateheat developed at an increased rate by the transformer. This includesVintake 36, pump 33, and discharge 37. One end of the 4 intake isconnected in iluid exchange relation with the lower portion of thecasing near the connection of lower conduit 23, and the other end of theintake is connected in iluid exchange relation with the pump. Thedischarge has its opposite ends connected in iluid exchange relationwith the pump and the opposite lower portion of the casing near theconnection of lower conduit 24. Baille 34 is attached to the bottom ofthe casing and extends upwardly to the proximity of baffle 31, therebyseparating the lower portion of the casing into two compartments, one ofwhich constitutes an intake compartment for the forced iluid system andthe other of which constitutes a discharge compartment of that system.This baille, however, is disposed in the casing so that it does notinterfere with the natural convection ilow of the cooling iluid since itis upstanding intermediate the two windings.

Self-cooling by natural convection results in substantially identicaliluid current paths on each side of this baille, and the direction ofiluid llow through the Winding is generally vertical, When thetransformer becomes heated, the fluid ilows by natural convectionupwardly through the transformer coils 17 and 18 and from the upperportion of the casing it enters the upper ends of radiators 13 and 14through iluid conducting conduits 21 and 22, respectively. That iluidpasses downwardly through the radiators as itcools, and then, of course,reenters the casing at the bottom thereof by passing through the loweriluid conducting conduits 23 and 24, respectively.

For forced cooling, that is, with the pump in operation, iluid is pumpedinto the casing from discharge 37. Some of this iluid passes upwardlythrough the winding while other of this iluid passes in a generallyparallel path upwardly through radiator 14. Then this iluid passes fromthe upper portion of coil 18 and from the top of radiator 14 to the lefthand side of the casing as viewed in Fig. 1 from which it is drawn bythe pump to the intake in generally parallel paths that have a directiondownwardly through the ducts in winding 17 and downwardly throughradiator 13. Under conditions when forced iluid circulation is requiredfor adequate cooling, it matters little whether the iluid circulatesthrough the radiator 14 upwardly from the bottom of the casing ordownwardly from the top ofthe casing as the temperature diierential ofthe iluid at the top and bottom of the casing is only a small percentageof the diilerential of temper- -ature of iluid pumped through theradiator and ambient, and it is this latter differential which is reliedupon to cool the iluid.

The arrows shown in the figures represent iluid circulated by the forcediluid system; the arrow head indicates the direction of flow.

In Fig. 2 a sectional View of a three leg shell type transformer istaken in a plane in front of an insulating washer 51 on which there areglued radiallydisposed spacers 52. Washers of this type are conventionalin transformers and provide ducts for insulating and cooling iluid topass between conventional adjacent disk coils (not shown). Thelcoolingducts are across the face of the washer between spacers 52.

Radiators 53 and 54 are connected to opposite sides of the casing 55 tobe in iluid exchange relation therewith. A baille 59 is attached to thesides of the casing intermediate the upper and lower connections to theradiators. This baille, like the horizontal bales of Fig. l, extendsfrom the sides of the casing approximately to the winding of thetransformer so as to influence the iluid to ilow through the winding.

' Intake 56 of the forced iluid system apparatus has one end thereofconnected in iluid exchange relation with the upper portion of thecasing and the other end thereof connected to pump 57, and discharge 58has its lower end connected in fluid exchange relation with the bottomportion of the casing 55 and its upper end connected to pump 57. Theintake and discharge are connected on 86, is illustrated in Fig. 4.

.Y nected thereto Vin huid exchange relation.

opposite sides of the horizontal bathe. `Lower leg .61 of the core mayalso constitute part of a baille upstanding from the bottom Vof Ythecasing which causes the fluid to how transverse the winding when pump 57is in operation, thereby improving the huid how into the winding andincreasing the dissipation of heat of the transformer.

The how of liquid by natural convection for the arrangement of Fig. 2 isconventional, taking similar paths on each side of the transformer,upwardly through the winding and into the radiators wherein it passesdownwardly as it cools before reenter-ing the casing at the bottomthereof.

When pump 57 is in operation, intake 56 draws huid upwardly through bothradiators, 53 and 54, and upwardly through the casing and transformerwinding. This fluid passes through the pump to be discharged into thebottom portion of the casing, whence it passes in parallel Vpathsupwardly through radiators 53 and 54 and upwardly through thetransformer. In addition to this upward flow, the :fluid howstransversely across the face of the washer because fluid discharged bythe pump is directed by the bathes and influenced by impedance of thepath through the winding to take the three parallel paths which meansthat some fluid Vmust traverse the transformer winding to get toradiator 53.

The view of transformer 66 shown in Fig. 3 is similar to that of Fig. 2,a shell type transformer disposed in similar relation to its casing 67.Bafhe 68 extends laterally between the transformer winding and the sidewalls ofthe casing approximately midway between the top and bottom ofthe casing. Lower leg, 71, of thercore may constitute part of a bailleat the bottom of the casing extending upwardly to the approximatevicinity of vthe outer periphery of winding 69. In this modificationonly one heat dissipating unit is shown. This is radiator 72, externalof the casing, disposed vertically with its upper end connected toheader 76 that is in fluid exchange relation with the upper portion ofthe casing above baille 68 and with its lower end connected to header 77that is in fluid exchange relation with the bottom portion of the casingbelow baille 68. In this embodiment the forced huid system apparatus isalso connected to these headers. Intake conduit 78 has its lower endconnected to header 77 and its upper end connected to pump 81, anddischarge conduit 79 has its upper end connected to header 76 and itslower end connected to the pump.

As in the previously described figures, the conventional how of coolinghuid 82 by natural convection in the transformer shown in Fig 3 is notAinterfered with by the provisions of the forced fluid system apparatus.For forced huid circulation the pump, of course, is in operation anddraws fluid from the casing on one side of bathe 68 and from one end ofthe radiator and discharges huid into the casing on the other side ofthat baille and into the other end of the radiator, thereby increasingthe flow of fluid through the radiator and increasing the cooling ehectof that huid in contact with the transformer. rIn this illustration theintake conduit 78 -draws fluid into header 77 from the bottom of theradiator 72 and from the bottom portion of the casing Vcausing fluid toflow downwardly through winding 69 past bathe 68 and transversely of thewinding above bathe 71. The fluid discharged by the pump .passes fromthe discharge conduit 79 into header 76 and from there in parallel pathsinto l radiator 72 and into the casing above baille 68.

Another shell type transformer, identified by number In the casing ofthis modification an upstanding baille 87 and a horizontal baille 88disposed around the coil 90 are like the similar baffles described inconnection with Fig. 3. Radiators 9S and 96 are disposed on oppositesides of the casing, being con- In this modillcation the forced fluidsystem apparatus includes,` lin addition to pump 91,'intak'e conduit I92and discharge conduit 93, a vertical baille 94 intermediate the top ofthe Winding and at least the top of the fluid vlevel in the casing tocause some fluid entering the casing from the pump discharge to flowcrosswise of the transformer wind ing. Further, the intake and dischargeof the pump are on opposite sides of the vertical bafhes 87 and 94 andon opposite sides of the horizontal 'baille 88. Intake 92 is connectedto the lower portion of the casing to the left of bathes 87 and 94, andthe discharge is connected to the upper portion of the casing to theright of bahles 87 and Vthe upper hal-f of 'the Winding (arrow 44).

94. Radiators 95 and 96 have their respective opposite ends connecteddirectly to the casing, and -preferably ythe upper ends of theseradiators connect with the casing at a fluid level below the point wheredischarge conduit 93 connects to the casing and the lower ends of theseradiators connect with the casing Vat a fluid level above the pointwhere the intake conduit 92 connects to the casing.

Preferably, the direction of flow of fluid through the radiators whenthe pump is in operation is conventionally downward. Fluid dischargedinto the lupper portion of the casing by the pump takes severalgenerally parallel paths, a feature common to the various embodiments ofthis invention. In one path some fluid hows downwardly into and throughradiator 96; Vin another path some of the lluid hows in a generallydiagonal direction downwardly through coil toward the intake conduit 92disposed in the :left hand bottom portion of the casing, and in a thirdpath huid traverses the upper portion of coil 90 below baille 94 andenters the upper end of radiator 95 through which this fluid passesdownwardly and is cooled. The fluid cooled in passing through radiator96 flows transversely through the lower half of coil 9d because thathuid is discharged from the radiator into the bottom right 4hand portionof the casing from which it is drawn across the winding above baille 87to the intake conduit 92.

In Fig. 5 the arrangement of the casing, the horizontal bathe, the lowerlvertical bathe, the radiators'and vthe pump 'and its associated intakeand discharge conduits is similar to the arrangement of those partsdescribed with respect to Fig. l. However, the transformer shown in Fig.5, is of the so-called shell type instead of core type of Fig. l, and abaille 97 is depended from the top of the casing to the approximatevicinity of the transformer core. Thus, this modification has thetransformer and baille arrangement shown in Fig. 4, but the pumpapparatus arrangement of Fig. l. The intake conduit of the pumpapparatus 99 is connected in fluid exchange relation with the casing onthe side of the lower upstanding baille opposite to the side of theconnection of the discharge conduit, but both the intake and dischargeof this apparatus are connected to the casing below the level of thebottom of the radiators. With the structure thus arranged, the pumpcirculates fluid transversely across the bottom portion of the windingabove the bottom upstanding batlle from the discharge conduit to theintake conduit as illustrated by arrow 41. Other'of the huid iscirculated upwardly in the casing directed by horizontal bathe 98 to-pass through the winding (arrow 42). Still other of the fluid (arrow43) is circulated up through vthe radiator which has its intake nearestthe discharge conduit of the pump, and from the upper end of thatradiator the fluid pumped through that radiator enters the upper portionof the casing and is deflected by baille 9'7 at the top of the casing soas to pass transversely of The pump apparatus draws fluid from thebottom left portion of the transformer which results in fluid beingdrawn inparallel paths, some huid (arrow 46) going into the top of theradiator to the left of the casing and other fluid (arrow 47) passingdiagonally downwardly through the winding in the casing. Thus, in thisarrangement the `huid circulated by the pump takes parallel pathsthrough the winding and one or the other radiator.

`sipation of the transformer heat.

Fig. 6 illustrates how the heat dissipating radiators may beincorporated into the casing by suitable bailling` Batlle or conduitmeans 101 are provided to separate the casing into a main portion 102holding the transformer 103 and auxiliary portions 104 and 106 throughwhich a cooling fluid such as an inert gas passes along heat dissipatingsurfaces 107 and 108, respectively. During selfcooling, the gas passesupwardly through the transformer in the main portion and downwardlythrough the auxiliary portions; whereas during forced ilow, pump 109discharges gas into the bottom right hand side of the casing and thehorizontal and vertical parts of the baille means cause thatrupwardlyilowing gas to be directed in parallel paths through the transformer andthrough auxiliary portion 106; Gas is drawn into the intake conduit 112of thc pump apparatus from auxiliary portion 104 and lfrom the left sideof the main portion.

In all the modiilcations embodying this invention, the construction ofthe transformer, the radiators and the 'pump may be such that theimpedances to the flow of llluid through the transformer and through theradiators and the head on the pump assure a considerable ilow of fluidthrough all those paths eilecting relatively fast dis- That is, theimpedance to iluid tiow preferably is generally balanced through the'casing and through the radiators.

Although but a few embodiments of the present invention have beenillustrated and described, it will be apparent to one skilled in the artthat various changes and modications may be made therein withoutdeparting from the .spirit kof the invention or from the scope of theappended claims.

It is claimed and desired to secure -by ILetters Patent: 1. `Incombination, a device including a casing containing an apparatus subjectto increases in temperature, -a radiator external of said casing, meansconnecting said radiator in iluid exchange relation with said casing,said device being substantially iilled with cooling lluid, said radiatordisposed with said means comprising an upper condui-t interconnectingthe upper end of said radiator to an adjacent upper portion of lsaidcasing and a lower conduit interconnecting the lower end of saidradiator to an adjacent lower portion of said casing whereby said fluidwhen heated flows 'by natural convection in series upwardly in saidcasing and downwardly in said radiator, and forced uid flow meansdisposed independently of said natural convection series fluid pathcomprising a conduit connected at its opposite ends to said device and afluid pump disposed intermediate said opposite ends to circulate saidiluid lfrom said pump through said casing and said radiator in Kthe samevertical direction Y in parallel paths.

2. In combination, a casing, an apparatus subject to increases intemperature disposed in said casing, said apparatus spaced from the topand opposite sides of said casing, la pair of radiators external of saidcasing, a iirst :of said radiators rconnected in uid exchange relationWith said casing at a first of said sides, a second of said radiatorsconnected in iluid exchange relation with said casing at the other ofsaid sides, said casing containing cooling iluid to a level above theconnections to said `radiators, baille means disposed in said casingintermedi- V.ate said opposite sides extending between said apparatusand said casing, whereby said iluid when heated has `natural convectionpaths upwardly in said casing `and Adownwardly in said radiators, andforced iluid -ilow means external of said casing disposed independentlyof said radiators including an intake conduit, a pump and a dischargeconduit, said intake connected in fluid exchange relation with'saidcasing on one side of said baille means, said discharge connected in uidexchange relation with said casing on the opposite side of said baillemeans, whereby said pump causes iluid to ilow :transversely in saidcasing.

3. In combination, a casing, an apparatus subject to 4'to saidradiators, baille means disposed in said casing intermediate saidopposite sides extending -between said apparatus and the bottom wall ofsaid casing, whereby said iluid when heated has similar naturalconvection paths on each side of said baille means upwardly in saidcasing and downwardly in said radiators, and forced tluid llow meansexternal of said casing disposed independently of said radiatorsincluding an intake conduit, a pump and a discharge conduit, said intakeconnected in iluid exchange relation with 4said casingon one side ofsaid baille means, said discharge connected in lluid exchange relationwith said casing on the opposite side of said baille means, whereby saidpump causes transverse iluid ilow in said casing, said intake disposedto draw -fluid from the bottom of a llrst of said radiators and theadjacent bottom portion of said casing, said discharge disposed to expeliluid into the bottom of the second of said radiators and the adjacentbottom portion of said casing under suil'icient head to cause some ofsaid ftluid to ilow upwardly through said second radiator and upwardlythrough said casing and whereby the lluid drawn from said irst radiatorby said intake enters said first radiator from the upper portion of saidcasing.

4. In combination, a casing, an apparatus subject to increases intemperature disposed in said casing spaced from one side of said casing,said apparatus provided with fluid passages therethrough, a radiatorexternal of said casing connected lat its top and bottom in Iiluidexchange relation with said casing, said casing containing cooling fluidat a level above the connections to said radiator, baille means disposedin said casing intermediate the top Iand bottom of said radiator betweensaid apparatus and said side to cause said fluid when heated to flow lbynatural convection upwardly in said casing through said fluid passagesin series hydraulic circuit with the downward tlow through saidradiator, and

forced fluid ilow means independent of said natural convection paththrough said radiator, said forcedY ilow means including an intakeconduit, a discharge conduit and a fluid pump connected between saidconduits, said intake connected in fluid exchange relation with saidcasing on one side of said baille means at a level as low as the bottomof said radiator, said discharge connected in fluid exchange relationwith said casing on the opposite side of said baille means at a level-as high as the top of said radiator to `cause fluid circulated by saidpump .to pass through both said apparatus and said radiator in hydraulicparallel paths.

5. In combination, a casing, an apparatus subject to increases intemperature disposed in said casing spaced from one side of said casing,said apparatus provided with iluid passages therethrough, a radiatorexternal of said casing connected -at its top and bottom in iluidexchange relation with said casing, said casing containing cooling tluidat a level above the connections to said radiator to cause said fluidwhen heated to ilow by natural convection upwardly in said casingthroughisaid fluid passages in series hydraulic circuit with thedownward -ilow through said radiator, Vand forced iluid ilow meansindependent of said natural convection path through said radiator, saidforced flow means including an intake, a discharge and a fluid pumpconnected between said intake and saiddischarge, said intake connectedin Iiluid exchange relation with said casing ata level as low as thebottom of said radiator, said discharge connected in fluid exchangerelation with -said casing at` a level as highfas the top ofv saidradiator to cause uid circulated by said pump to pass through `both saidapparatus and said radiator in hydraulic parallel paths.

6. In combination, a casing, an apparatus subject to increases intemperature disposed in said casing and spaced from the top and oppositesides of said casing, a pair of radiators external of said casing', afirst of said radiators connected in fluid exchange relation with saidcasing to a rst of said sides, a second of said radiators connected influid exchange relation with said casing to the other of said sides,said casing containing cooling uid to a level above the connections tosaid radiators, whereby saidv fluid when heated has natural convectionpaths upwardly in said casing through said apparatus and downwardly insaid radiators, and forced uid means external of said casing disposedindependently of said radiators including an intake, a pump and adischarge, said intake connected in uid exchange relation with saidcasing near the bottom portion of said rst side to draw uid from thebottom of said first radiator and from the adjacent bottom portion ofsaid casing, said discharge connected in fluid exchange relation withsaid casing near the bottom portion of said other side to expel uid intothe bottom of said second radiator and the adjacent bottom portion ofsaid casing.

7. In combination, a casing, an apparatus subject to changes intemperature disposed in said casing, said apparatus having fluidpassages therethrough, a pair of radiators external of opposite sides ofsaid casing, a rst of said radiators connected in fluid exchangerelation with said casing to a iirst of said sides, a second of saidradiators connected in fluid exchange relation with said casing to theother of said sides, said casing containing cooling fluid to a levelabove the connections to said radiators, bafle means disposed in saidcasing intermediate the top and bottom of said casing extending betweensaid apparatus and said opposite sides, and forced uid ow means externalof said casing disposed independently of said radiators including anintake, a pump and a discharge, said intake connected in iluid exchangerelation with said casing to one side of said bafe means, said dischargeconnected in uid exchange relation with said casing to the opposite sideof said bale means, the head on said pump being suicient when said pumpis in operation that uid discharge from said pump will flow in parallelpaths through the passages in said apparatus and through said radiators.

8. In combination, a casing, an apparatus subject to changes intemperature disposed in said casing spaced from the top and oppositesides of said casing, a radiator external of said casing connectedthereto at its opposite ends in fluid exchange relation at the top andbottom portions of a side of said casing, said casing containing coolingfluid to a level above the connections of said radiator to said casing,baffle means disposed in said casing intermediate the top and bottom ofsaid casing extending between said Iapparatus and said sides, and forceduid low means external of said casing disposed independently of saidradiator including an intake, a pump and a discharge, said intakeconnected in fluid exchange relation with said casing lat a level ashigh as the top of said radiator, said discharge connected in uidexchange relation with said casing at a level as low as the bottom ofsaid radiator, whereby uid circulated by said pump passes through bothsaid apparatus and said radiator.

9. In combination, a casing, an apparatus subject to increases intemperature disposed in said casing, said apparatus spaced from the topand opposite sides of said casing, a pair of radiators external of saidcasing, a rst of said radiators connected in uid exchange relation withsaid casing at a rst of said sides, a second of said radiators connectedin uid exchange relation with said casing at the other of said sides,said casing containing a cooling fluid to a level above the connectionsto said radiators, bafde means disposed in said casing intermediate saidopposite sides extending between said apparatus and the 10 top of saidcasing, wherebyV said u'id when heated has similar natural convectionpaths on each side of said baie means upwardly in said casing anddownwardly in said radiators, and forced fluid flow means external ofsaid casing disposed independently of said radiators including anintake, a pump and a discharge, said intake connected in uid exchangerelation with said casing on one side of said bae means, said dischargeconnected in fluid exchange relation with said casing on the oppositeside of said baie means, whereby said pump causes fluid to flowtransversely in said casing, said intake disposed to draw fluid from thebottom of said first radiator and the adjacent bottom portion of saidcasing, said discharge disposed to expel uid into the top of said secondradiator v and the adjacent top portion `of said casing.

l0. In combination, a casing, an apparatus subject to increases intemperature disposed in said casing, said apparatus spaced from the topand opposite sides of said casing, a pair of radiators external of saidcasing, a first of said radiators :connected in fluid exchange relationwith said casing at a rst of said sides, a second of said radiatorsconnected in uid exchange relation with said casing at the other of saidsides, said casing containing cooling uid to a level Iabove theconnections to said radiators, baffle means disposed in said casingintermediate said opposite sides extending between said apparatus andthe top of said casing, whereby said uid when heated has similar naturalconvection paths on each side of said bafe means upwardly in said casingand downwardly in said radiators, and forced uid flow means external ofsaid casing disposed independently of said radiators including anintake, a pump and a discharge, said intake connected in uid exchangerelation with said casing on one side of said baille means, saiddischarge connected in iiuid exchange relation with said casing on theopposite side of said baffle means, whereby said pump causes fluid to oWtransversely in said casing.

ll. In combination, a casing containing cooling fluid, an apparatussubject to changes of temperature disposed in said casing, a heatexchanger disposed outside said casing and connected in fluid exchangerelation at its opposite ends to the top and bottom of said casing, saidapparatus being provided with fluid passages therethrough to cause saidliuid when heated to ow by natural convection upwardly in said casingthrough said iluid passages in series hydraulic circuit with thedownward flow through said heat exchanger and a forced fluid meansconnected in uid exchange relation with said casing, said forced iluidmeans including a uid pump external of said casing and independent ofsaid heat exchanger so as not to interfere with natural convection flowof said uid when not in operation and being disposed in fluid exchangerelation with said casing and said heat exchanger so as to cause uid toflow in the same vertical direction in hydraulic parallel paths throughsaid passages and said heat exchanger when said pump is in operation dueto the relative impedance to fluid ow in said two hydraulic parallelpaths.

12. In combination, a device including a casing containing an apparatushaving fluid passages therethrough and subject to changes oftemperature, said device substantially filled with cooling uid andhaving a radiator external of said casing and means connecting oppositeends of said radiator in fluid exchange relation with the top portionand bottom portions of said casing to cause said llui-d when heated toflow by natural convection in series hydraulic circuit upwardly in saidcasing and downwardly in said radiator, the impedance to uid ilow insaid casing being approximately equal to the impedance to uid ow in saidradiator, and forced fluid flow means comprising a conduit connected atits opposite ends to said device and including a duid pump disposedintermediate said last mentioned opposite ends, said pump when inoperation having sucient head to force said 11` uid to 110W through saidcasing and said radiator in the same vertical direction in hydraulicparallel paths.

13. In combination, a casing containing a cooling fluid,

an apparatus subject to increases in temprature' disposed in the samevertical direction as the forced flow of uid 15 through said exchanger,said forced uid ow means being external of said casing and independentof said exchanger so as not to interfere with naturalconvection of saidfluid when said ovv means is not in operation.

References Cited in the le of this patent UNITED STATES PATENTS1,706,574 Hodtumv Mar. 26, 1929 1,798,702 Y Roebel Mar. 31, 19311,800,163 Thompson Apr. 7, 1931 2,347,989 Burnham May 2, 1944 FOREIGNPATENTS l 348,794 Germany Feb. 18, 1922 France Nov. 9, 1927

